Question about a driver rotation expression
Rotating how much?  What about when thigh bone isn't rotated that much?
The form of a single line &quot;If&quot; is something like the following:
((var * constant1) * (var&gt;(30.1 * pi/1800))) + ((var * constant2) * (1.0- var&gt;(30.1 * pi/180)))
What that's saying:
a) If var's rotation is greater than 30.1 degrees, output var * constant1.
b) Else, output var * constant2.
Constant2 can be zero.  You can understand this by recognizing that a statement like var&gt;n returns 1 if the statement is true and 0 if it is false.  Multiplying 1.0 - whatever instead of flipping &gt; for &lt;= is just style in this case, but it's style informed by the situations where the things you're measuring aren't exactly 0 or 1.
And the reason for var&gt;(30.1*pi/180) is because, for drivers, you're working with radians, not degrees.  (Don't ask me why, it's a developer decision than I don't necessarily agree with.)